Conventionally, this kind of coupling fixture, as shown in FIGS. 7 and 8, is provided with a cylindrical outer ring A and a cylindrical inner ring B each having a cut, the outer ring A being provided at both axial sides of the inner periphery thereof with tapered surfaces T1 and T2, the inner ring B being provided at both axial sides of the outer periphery thereof with tapered surface T3 and T4 opposite to the tapered surfaces T1 and T2 respectively, between the outer ring A and the inner ring B and at one axial side is interposed an annular ring nut C circumferentially continuing and having at the outer and inner peripheries thereof tapered surfaces T5 abutting against the tapered surfaces T1 and T3 respectively, between the rings A and B and at the other axial side is interposed an annular ring washer D circumferentially continuing and having at the inner and outer peripheries thereof surfaces T6 abutting against the tapered surfaces T2 and T4 respectively.
The ring washer D has at a plurality of circumferential portions axially through bores a and the ring nut C is provided at a plurality of portions opposite to the through bores a with a plurality of threaded bores b, first screw bolts E1 for tightening are inserted into the through bores a and threaded bores b respectively, a plurality of threaded bores c are formed at the portions on the ring washer D not opposite to the threaded bores b so as to insert second screw bolts E2 into the bores c respectively. Also, the tapered surfaces T1 through T6 provided at the outer ring a, inner ring B, ring nut C, and ring washer D each are set at a cone angle of about 7.degree. through 15.degree. in order to get a large wedgewise coupling force, in other words, to increase a press-containing force, with a small tightening force when the first screw bolts E1 tighten the ring nut C and ring washer D.
In a case where the above-mentioned coupling fixture is used to couple a gear G onto a shaft F, as shown in FIG. 7, the outer ring A and inner ring B are interposed between the inner periphery of a recess g provided at the gear G and the outer periphery of the shaft F, the first screw bolts E1 are screwably tightened to move the ring nut C and ring washer D close to each other, and the tapered surfaces T5 and T6 urge the tapered surfaces T1 and T3, and T2 and T4, so that the outer ring A is expanded in diameter to be brought into press-contact with the inner periphery of recess g and the inner ring B is contracted in diameter to be brought into press-contact with the outer periphery of shaft F, thereby integrally coupling the gear G with the shaft F.
The outer and inner tapered surfaces T5 of the ring nut C are rigidly coupled in wedge connection with the tapered surfaces T1 and T3 at the outer and inner rings A and B and the inner and outer tapered surfaces T6 of the ring washer D are coupled with the tapered surfaces T2 and T4 at the outer and inner rings A and B in the same manner as the above, so that the gear G is rigidly coupled with the shaft F, but when the gear G is dismantled therefrom, the rigid wedge connection should be released. Therefore, at first, the first screw bolts E1 are unscrewed and then, as shown in FIG. 8, the second screw bolts E2 are screwably inserted into the threaded bores c respectively and abut at the tips against the end face of ring nut C, the screw operation is repeated several times to thereby outwardly dismantle, by means of screw thrust, the washer D from the tapered surfaces T2 and T4 at the outer and inner rings A and B. After the ring washer D is dismantled, the previously unscrewed first screw bolts E1 are again screwed into threaded bores b and then hit on the heads to outwardly remove the ring nut C from the tapered surfaces T1 and T3, thereby eliminating the urging forces of the outer and inner rings A and B with respect to the gear G and shaft F so as to dismantle the gear G therefrom.
At such a coupling fixture, when the shaft F and gear G are tightly coupled as the above-mentioned, and thereafter dismantled from each other, in order to dismantle the rigidly coupled ring washer D from the outer and inner rings A and B, a problem is created in that the second screw bolts E2 are specially required and a complicated removal work is required as the above-mentioned.